Introducing cultivars of yellow lupine that tolerate delays in the sowing dates (thermoneutral) or ones that ripe faster (self-completing) into agricultural practice makes it possible to broaden the cultivation of this agriculturally valuable species. The aim of the study was therefore the determination of the effect of the sowing date on the size and quality of the seed yield of yellow lupine in the mountain-foot region. It was hypothesized that cultivars Mister (conventional) and Taper (self-completing) would react differently to the applied study factor. Strict experiment was carried out in years 2011-2013 at the Cultivar Assessment Experimental Station in Dukla on 5^th class soil of mountain oat-potato complex. Sowing date and diversified weather conditions in the study years had a significant effect on plant growth and development. The highest plant density before harvest was obtained on the second sowing date (second ten days of April), and the lowest on the first sowing date (first ten days of April), which was statistically significant. Sowing dates significantly modified such yield characteristics as the number of grains per pod and mass of 1000 grains, whereas the number of pods per plant was constant. On average in the study years, significantly higher yield was obtained after sowing the seeds in the first twenty days of April than in the last ten days of April. This relation was not, however, repeated in the study years. With the delay in the sowing date, total protein content in the seeds decreased. Cultivar Mister in comparison with cultivar Taper was characterized by a significantly higher pod number per plant, mass of 1000 grains, and seed yield. It was also proved that cultivar Mister contains significantly more crude fat in the seeds than cultivar Taper. Established percentage of total protein, ash, and fibre was not diversified between the studied cultivars.

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